Throw the multimeter in the bin - it must be faulty.

Seriously, though, deciBels (dB) are always relative to something. Absolute levels are measured in units such as dBu or dBm or dBV. Your recorded tracks are probably -20 dB to -15 dB relative to full-scale on your interface, so they are a good level to be working at. If full scale is (say) +24dBu, then when your tracks are output via your interface's D-A converters, the absolute levels will be +4 to +9 dBu. The multimeter will have a different idea of what its 0dB is, unless it happens to know about dBu or dBm, when it would read +4 to +9 dB for the above example.

So to make sense of your readings, you have to know (1) the full-scale level of your interface (0dBFS) in dBu, and (2) what 0dB represents on the multimeter in dBu. If the answer to (1) is X dBu and the answer to (2) is Y dBu, then you have to add (Y - X) to your multimeter readings to read the same as in your DAW. Note, however, that most multimeters are calibrated for sinewaves using a form factor (rms/mean) of 1.11, and will not give the same levels as your DAW (even after the correction) for typical music signals. This is not the case for "true r.m.s." multimeters, when the readings should agree with your DAW after the level correction.

I understand, thanks.

So how can I learn my interfaces full scale dB? I have searched the net and the manual but couldn't find any info on it. It's knob can be adjusted from 0dB to 53dB. I use a Motu 828mk3 by the way.

Or what my -3dB actually is in terms of dBu? So I actually am a little confused what should I do step by step?

Thanks very much for your time again, I really appreciate it.

MOTU play silly B's with web access to even basic technical information about their products - when will they learn that unavailability of information is a huge disincentive to buying their gear? The result is that I don't know what 0dBFS represents in dBu on the DAC outputs of the 828 Mk3.

One thing you could try is to generate a 100Hz sinewave in your DAW and then normalize it. You will need either a minute or two of it, or else select a section that is an exact multiple of 10ms for replay. When you play it via a DAC in the 828, it will automatically be at 0dBFS, and your meter should show a steady reading. Call this reading A. Now when your music shows -20dB in the DAW and the meter shows a reading B, the equivalent sinewave figure would be A-20, so by seeing how close B is to (A-20), you can make a wild guess at what correction factor to apply for your type of music.

This will not tell you what the 0dBFS on the 828 and 0dB on the meter are in absolute dBu, but it will give you the relative levels.

Why are you so worried about it anyway?

Ok I have tried what you said and yes it was steady at 0dB in my Logic's Multimeter. So it means 0dBFS is equal to 0dB. And things are correct, am I right?

And finally when the Multimeter reads lets say -20dB - -15dB when I'm recording it's a healthy measure in terms of dBu right?

And I'm worried because I constantly feel unsecure and bothered when I feel not in control of everything or not knowleged about what I do.

So this is the level meter inside Logic and not a separate hardware multimeter you were using to measure the output? No wonder you were confused about what I wrote! Your levels sound healthy enough, but don't forget that recording levels are on a per-track basis, and many tracks mixed together without attenuation may add up to more than 0dBFS.

Boswell, post: 349951 wrote: don't forget that recording levels are on a per-track basis, and many tracks mixed together without attenuation may add up to more than 0dBFS.

Spot on Bos! This is where all the problems start.

Hmm, I see thanks a lot it was a big relief.

Other than that I remember reading that maximum level of a master output should be maximum -3dB or so. And since my 0dB is equal to 0dBFS I guess it never should go above 0dB, right? But since you said many tracks added together can go above 0dBFS, I'm confused again :-)

What it means is that you have to bring down all the track faders by the same amount, so the mix balance is not altered but the final mix level is reduced to the required figure below 0dBFS.